Transcript Bacteria - Hobbs High School

Prokaryotes
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General information
General structures/functions
Reproduction (binary fission)
Genetic recombination mechanisms: conjugation, transformation,
transduction
Endospore production
Modes of nutrition: aerobic vs. anaerobic & autotrophs vs.
heterotrophs
Free-living vs. symbiotic types of bacteria
Diseases & treatment
DOMAIN Bacteria
– Bacteria
– Cyanobacteria
• DOMAIN Archaea - methanogens, halophiles, thermoacidophiles
Prokaryotes
• Prokaryote – lack nucleus and various organelles (do
have ribosomes)
– Oldest and most simplest forms of life
• Two Domains (molecular/cellular differences):
Bacteria & Archaea
• Previously placed in Kingdom Monera
• Widely distributed in nature:
– Soil, water, air, etc.
• Most abundant of any organism
– 1 gram of soil = 100 million bacteria cells
• Tiny, unicellular organisms: 1 µ m to 10 µ m (1 µ m =
1/1,000,000 m)
• Structures associated with bacteria
– Nucleiod - contains single circular strand of DNA
– Plasmid - accessory ring of DNA (used by scientist for
Cytoplasm
genetic engineering)
– Ribosomes - responsible for protein synthesis
– Plasma Membrane - acts as a barrier between the
internal and external environment
Cell
– Cell Wall - surrounds plasma membrane (composed of
Envelope
peptidoglycan)
– Capsule/Slime Layer - surrounds cell wall; protective
– Pili - short hair-like structures for adhesion to surfaces
Appendages
– Flagellum - whip-like projection; gives cell motility
• Reproduction - asexual thru Binary Fission
– Daughter cells genetically identical to parent
Parent
Daughter Cells
Genetically the
same as the original
parent cell
• DNA variations occur via genetic recombination
(NOT binary fission)
– Transformation - incorporates DNA from the
environment into genome
– Conjugation - transfer of genetic information from
one cell to another via “sex” pili
– Transduction - bacteriophages transfer bacterial DNA
from one cell to another
Ways that bacteria can develop
antibiotic resistance
Transformation
Transduction
• Endospores are formed by some
bacteria when exposed to hostile
environment
Some hardy for
years!
– Purpose: survival – not reproduction
– When conditions become “friendly”
again the cell become active
• Anthrax & Botulism are conditions
resulting from organisms that
generate endospores; Toxins release
produce symptoms of these
diseases.
• Means of Nutrition
• Environmental conditions required for
metabolism (cellular respiration) to occur vary
– Obligate anaerobes - survives only when free
oxygen NOT present
– Facultative anaerobes - grows either in presence or
absence of free oxygen
– Aerobes - requires free oxygen to be present
• Modes of nutrition also vary
– Autotrophs
• photosynthesizers = cyanobacteria
• chemosynthesizers = archaeabacteria
– Heterotrophs = most bacteria
• MOST are free-living heterotrophs
• Ecological (Environmental) Importance:
– Saprotrophs/decomposers – live off dead organic material
– Important in recycling nutrients in ecosystems.
• Economic Importance:
– Used to make: alcohols, acetic acid, acetones, antibiotics
– Used to make food: cheeses, butter, sauerkraut
• SOME develop symbiotic relationships
1.Mutualism - both bacteria and host benefit
(e.g. nitrogen-fixing bacteria in roots)
2.Commensalism - bacteria benefits and other
is not harmed nor benefits
3. Parasitism - bacteria causes harm to host (e.g.
causes diseases aka “pathogens”)
• Examples of diseases:
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STDs – syphilis, gonorrhea
Respiratory Disease – strep throat, scarlet fever, tuberculosis
Skin Disease – boils, pimples
Digestive tract disease – food poisoning, dysentery, cholera
Nervous system disease – botulism, tetanus, leprosy
Systemic disease – plague, typhoid fever
Other – Lyme disease
• Treatment/Prevention:
– Antibiotics – inhibit cell wall synthesis or inhibit protein
synthesis - targets prokaryotic cells and not eukaryotic cells
– Public awareness – good food prep, handwashing
– Vector control – fleas, ticks, etc
• DOMAIN Bacteria
• Bacteria – commonest type of prokaryote
• Three Basic Shapes:
– Bacillus = rod
– Coccus = round
– Spirillum = curved/spiral/helical
Prokaryotes - Cell Wall & Gram Stain
• Cell wall maintains cell integrity and composed of peptidoglycan
– polysaccharides cross-linked w/ peptides (various lengths)
• Archaea do not have peptidoglycan, some have pseudopeptidoglycan –
pseudomurein
• Composition of cell wall is basis of Gram stain
– thick layer of peptidoglycan = stain positive - purple
– thin layer of peptidoglycan = counter stain - red
Prokaryotes - Cell Wall & Gram Stain
• Gram-positive bacteria have thick peptidoglycan layer
– teichoic & lipoteichoic acids embedded in wall
• Gram-negative bacteria have thin peptidoglycan layer
– additional outer membrane with lipopolysaccharide & porins
• Cyanobacteria (old terminology blue-green algae)
– May appear other colors: red, yellow, brown
– Environment: aquatic or moist surfaces
– Autotrophic via photosynthesis
• Photosynthetic pigments found in thylakoids (NOT CHLOROPLAST)
• * Thought to have released free oxygen in earth’s primitive atmosphere
– May live singly, in colonies or be filamentous
• Unicellar form – e.g. Gloeocapsa
• Colonial form – e.g. Anabena
• Filamentous form- e.g. Oscillatoria
– Lack visible means of locomotion
– Some have heterocysts that ‘fix’ atmospheric nitrogen (e.g. Anabaena)
– First in aquatic food chain (producers)
• * Thought to be first colonizers of land
– Some form symbiotic relationships (e.g. with fungi = LICHENS;
important to soil formation)
– Associated with pond/lake “blooms” and fish kills
• DOMAIN Archaea
– Composition of cell wall different than in other
types of bacteria
– Different ribosomal RNA nucleotide base
sequencing than other bacteria.
– Share more similarities to Domain Eukarya than
other bacterial types
– Plasma membrane has high lipid content
– Most are autotrophic via Chemosynthesis
– These prokaryotes live in extreme environments
(similar to primitive earth).
• Examples of Archaeabacteria:
– Methanogens - produce methane gas
• GI tract of some animals, swamps, marshes
– Halophiles - survive in salty environments (12 –
15% NaCl)
• Great Salt lake and Dead Sea
– Thermophiles - loves acid conditions & extreme
heat
• Hot springs, geysers, thermal vents
– None known to be parasitic